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Affected by thermal perturbation due to mantle uprising, the rheological structure of the lithosphere could be modified, which could lead to different rifting patterns from shelf to slope in a pas-sive continental margin. From the observed deformation style on the northern South China Sea and analogue modeling experiments, we find that the rift zone located on the shelf is characterized by half grabens or simple grabens controlled mainly by long faults with large vertical offset, supposed to be formed with normal lithosphere extension. On the slope, where the lithosphere is very hot due to mantle upwelling and heating, composite grabens composed of symmetric grabens developed. The boundary and inner faults are all short with small vertical offset. Between the zones with very hot and normal lithosphere, composite half grabens composed of half grabens or asymmetric grabens formed, whose boundary faults are long with large vertical offset, while the inner faults are relatively short. Along with the thickness decrease of the brittle upper crust due to high temperature, the deformation becomesmore sensitive to the shape of a pre-existing weakness zone and shows orientation variation along strike. When there was a bend in the pre-existing weakness zone, and the basal plate was pulled by a clockwise rotating stress, the strongest deformation always occurs along the middle segment and at the transition area from the middle to the eastern segments, which con-tributes to a hotter lithosphere in the middle segment, where the Baiyun (白云) sag formed.
Affected by thermal perturbation due to mantle uprising, the rheological structure of the lithosphere could be modified, which could lead to different rifting patterns from shelf to slope in a pas-sive continental margin. From the observed deformation style on the northern South China Sea and analogue modeling experiments, we find that the rift zone located on the shelf is characterized by half grabens or simple grabens controlled mainly by long faults with large vertical offset, supposed to be formed with normal lithosphere extension. hot due to mantle upwelling and heating, composite grabens composed of symmetrical grabens developed. between the zones with very hot and normal lithosphere, composite half grabens composed of half grabens or asymmetrical grabens formed , whose boundary faults are long with large vertical offset, while the inner faults are more short. Alon g with the thickness decrease of the brittle upper crust due to high temperature, the deformation becomes more sensitive to the shape of a pre-existing weakness zone and shows orientation variation along strike. and there was a bend in the pre-existing weakness zone, and the basal plate was pulled by a clockwise rotating stress, the strongest deformation always occurs along the middle segment and at the transition segment from the middle to the eastern segments, where con-tributes to a hotter lithosphere in the middle segment, where the Baiyun ( White cloud) sag formed.